High strength hot-press die



ec.29,19? P. A. ORMSBY ET AL HIGH STRENGTH HOT-PRESS DIE Filed Dec. 31, 1968 Phillip A. Ormsby Eflwberi C. Thompsonm,

INVENTORS.

United States Patent O 3,550,213 HIGH STRENGTH HOT-PRESS DIE Phillip A. Orrnsby, Huntsville, and Ethbert C. Thompson III, Redstone Arsenal, Ala., assignors to the United States of America as represented by the Secretary of the Army Filed Dec. 31, 1968, Ser. No. 789,040 Int. Cl. B29c 1/02 U.S. CI. 1847 6 Claims ABSTRACT OF THE DISCLOSURE A high strength hot-press die composed of a conventional graphite inner die encased by a filament wound high strength graphite fiber. The high strength graphite fiber is filament wound on the conventional graphite inner die, and by the use of polymeric binders that will convert to carbon or graphite during bake out cycles, the fibers can be wrapped with suificient tension to induce a compressional load into the inner die wall. This prestress condition will have to be overcome during actual pressing operations before tensional failure can occur in the die wall.

BACKGROUND OF THE INVENTION This invention is in the field of dies for hot-pressing ceramics or other high temperature mateirals. A problem with the hot-press dies currently in use is that the die wall tensile strength limits the compressive loads that can be used in pressing operations. A conventional graphite die wall is limited by its hoop tensile strength to approximately 4,000 p.s.i., with a compressive strength capability of approximately 15,000 to 18,000 psi, for the die plungers.

SUMMARY OF THE INVENTION BRIEF DESCRIPTION OF THE DRAWING The single figure shown in the drawing is a perspective View of the die and plungers.

PREFERRED EMBODIMENT OF THE INVENTION The figure shows a high strength hot-press die including a conventional graphite internal die 1. Reference numeral Patented Dec. 29, 1970 2 indicates the high strength graphite fibers such as Thornel fibers. The fibers are wound around die 1 and caused to adher to the die by using appropriate polymeric binders, such as pre-polymerized furfural alcohol resin or acenapthylene resin that will convert to carbon or graphite during special high temperature (1000-2500" C.) bake out cycles. The fibers are wrapped around die 1 with sufficient tension (3 to 5 lbs/ply) to induce a compressional pre-load into the die wall. This prestress condition will have to be overcome during any actual pressing operations with the composite die before any tensional failure can occur in the die wall. The relative high tensile strength of the fibers will also provide significant structural support to the die wall. Numeral 3 shows the laminated graphite cloth composite plungers. Through the use of this special composite graphite die the tensile strength of the die wall has been increased to over 50,000 p.s.i. (from nominal 4,000 p.s.i.) and the compressive strength of the plungers accordingly has been increased to over 40,000 p.s.i. (from nominal 18,000 p.s.i.). These strength increases result in improvement of maximum operating pressures of up to 800 percent over the conventional non-reinforced solid graphite dies.

We claim:

1. A high strength hot-press die comprising an inner graphite die encased by a high strength graphite fiber wound around the inner die and bound thereto by a binder.

2. A die as set forth in claim 1 wherein said graphite fiber is tensionally wound to induce a compressional preload into the die wall.

3. A die as set forth in claim 2 in combination with laminated graphite cloth composite plungers.

4. A die as set forth in claim 2 wherein said binder is pre-polymerized furfural alcohol resin.

5. A die as set forth in claim 2 wherein said binder is acenapthylene pitch.

6. A method of producing a high strength hot-press die which method comprises: wrapping high strength graphite fibers around an inner graphite die; inducing a compressional pre-load into the die wall and bonding the fibers to the die wall. f

References Cited UNITED STATES PATENTS 3,177,084 4/ 1965 Amstein 18-47X JAMES M. MEISTER, Primary Examiner U.S. Cl. X.R.

Notice of Adverse Decision in Interference In Interference No. 98,256 involving Patent No. 3,550,213, P. A. Ormsby and E. C. Thompson, HIGH STRENGTH HOT-PRESS DIE, final jud ment adverse to the patentees was rendered May 16, 1974, as to claims 1, 2 an 6.

[Ofiioz'al Gazette 0 f September 24,1974] 

